In general, in order to form a large number of sheet display devices such as organic EL display devices or the like by use of a mother substrate, the following method is used. A resin film formed of polyimide or the like is formed on the mother substrate, and a plurality of organic EL elements including a plurality of thin film transistors (TFTs), a light emitting layer and a gas barrier layer are formed on the resin film. Then, the substrate is cut into a plurality of substrate portions by a glass scribe method or the like, and the resin film is peeled off from the substrate portions to produce a plurality of organic EL display devices. As such a mother substrate, a glass substrate is used, for example.
However, the resin film is thin and elastic, and cannot be easily cut together with the glass substrate by the glass scribe method. It is not easy either to peel off the resin film from the glass substrate. Therefore, there is a problem that in a step of cutting the glass substrate or a step of peeling off the resin film from the glass substrate, the resin film formed on the glass substrate is pulled, which damages the TFTs and the organic EL elements formed on the resin film.
In addition, it is difficult to make small the tolerance for the cutting position at which the glass substrate is to be cut. For these reasons, a production method capable of enlarging the margin for the cutting position of the glass substrate and thus providing a high yield is desired.
According to an existing method proposed for this purpose, a groove is formed by laser light in a resin film along a line along which the glass substrate is to be cut before the glass substrate is actually cut, and then a scribing unit is directed to the groove formed on the resin film in order to cut the glass substrate by the scribe method.
With reference to FIG. 1 and FIG. 2, an example of such a method for producing a conventional organic EL display device will be described. As shown in FIG. 1A, a first resin film 20 is formed on a first glass substrate 10, which is a TFT-side mother substrate. An organic EL layer 40, a sealing member 44, a filling member 42, a line 30 and the like are formed on the first resin film 20. A second resin film 22 is formed on a second glass substrate 12, which is a counter substrate-side mother substrate. On the second resin film 22, a gas barrier layer 24 may be formed. Although not shown, a gas barrier layer may also be formed on the first resin film 20.
From the structure shown in FIG. 1A, individual organic EL display devices are produced as follows, for example. First, from the state shown in FIG. 1A, an interface between the second glass substrate 12 and the second resin film 22 is irradiated with laser light to remove the second glass substrate 12.
Next, as shown in FIG. 1B, the first resin film 20 and the second resin film 22 are irradiated with light from a solid UV laser to cut the first resin film 20 and the second resin film 22.
Next, as shown in FIG. 10, an excessive portion of the first resin film 20 and the second resin film 22 is removed.
Next, as shown in FIG. 2A and FIG. 2B, an excessive portion of the first glass substrate 10 (on the TFT side) is cut away by the glass scribe method.
Next, an interface between the first glass substrate 10 and the first resin film 20 is irradiated with laser light to remove the first glass substrate 10.
As a result, individual organic EL display devices 1000 as shown in FIG. 2C are produced.
For example, Japanese Laid-Open Patent Publication No. 2011-227369 describes the following. In a resin film provided on a mother substrate, one groove along which the resin film is to be cut is formed. After the mother substrate is peeled off, a plastic substrate is bonded to the resin film. Then, the plastic substrate is cut along the groove formed in the resin film.
According to this method, only one groove is formed in the resin film. Therefore, there is a problem that in the case where the cutting position at which the glass substrate is cut is offset, the resin film is pulled, which may damage display elements formed on the resin film.